The present invention relates generally to the production of reservoir fluids, and particularly to a well construction technique that utilizes an insertion guide placed in an open-hole section of a wellbore.
In the conventional construction of wells for the production of petroleum and gas products, a wellbore is drilled through a geological formation to a reservoir of the desired production fluids. For a variety of reasons, e.g. local geology and strength of formation, tortuosity of the well, quality of drilling fluid, diameter of tubing, etc., the usable diameter of the wellbore tends to decrease with depth. Consequently, the suite of casings, liners and/or completion tubulars becomes sequentially smaller in diameter when progressing downhole. The diameter reduction is necessary both to compensate for the narrowing usable space of the wellbore in the open-hole section of the well and to permit insertion of the latest tubular through the previous tubular. In many cases, the diameter of the subsequent tubular element must be at least one and a half inches smaller than the inside diameter of the open-hole section of the well.
The diameter reduction generates an open-flow annulus between the formation or wellbore wall and the tubular component. Generally, this open-flow annulus is undesirable. Outside the reservoir region, the open-flow annular space often is cemented to provide isolation between the formation and the adjacent tubular component. This avoids corrosion of the tubular component, axial migration of liquids and gas along the annulus and other undesirable effects.
Within the reservoir region, hydraulic communication from the formation to the wellbore is necessary for the production of the reservoir fluids. The open-flow annular space can be cemented or kept open. When this annular is cemented, the formation is later put back in communication with the wellbore by perforating the casing and the cement sheath. This technique permits good isolation of different intervals of the reservoir. If this annular is not cemented, we can maximize the contact between the formation and the wellbore but then it becomes much more difficult to get isolation between different intervals. In both cases, cemented or not cemented, the loss of diameter of the completion relative to the diameter of the open hole can be detrimental to maximizing productivity of the well. For example, if the completion is a slotted liner or sand control screen, the necessarily smaller diameter of the liner or screen reduces the section available for flow. Also, as mentioned above, the presence of the open annulus creates difficulty in isolating specific intervals of the formation. As a result, selective sensing of production parameters as well as selective treatment, e.g. stimulation, consolidation or gas and water shut-off, of specific intervals of the formation is difficult, if not impossible. Additionally, in certain wells prone to sand production, the particulates can freely wash along the annulus, repeatedly hitting the completion and causing wear or erosion of the completion.
Because of these problems, most operators continue to cement and perforate casings and liners set in reservoirs so as to allow repair of well problems over the life of the well. Completions, such as slotted liners and screens, are only used in cases where production problems are not anticipated or where cost is an issue. Some attempts have been made to minimize diameter reduction from one piece of tubular to the next and to eliminate or reduce the open annulus without resorting to cementing, but the attempts have met with limited success.
For example, one method is to simply improve the drilling and well conditions to minimize diameter reduction. Such improvement may include controlling the well trajectory and selecting high performance muds. Although this approach may slightly reduce the size of the open annulus surrounding the completion, a substantial open annulus still remains.
Another attempt to alleviate the problems of diameter reduction and open annulus involves drilling new sections of the wellbore with a larger diameter than the previous tubular. This can be achieved with a bi-center bit, for example. With the increased diameter of the subsequent wellbore portion, the next succeeding section of tubular can be provided with an outside diameter very close to the inside diameter of the previous tubular. However, the open-flow annulus in the open-hole section of the wellbore still remains.
More recently, expandable tubular completions have been introduced. In this approach, a tubular completion is inserted into an open-hole section of the wellbore in a reduced diameter form. The completion is then expanded against the formation, i.e. against the open-hole sides of the wellbore. This approach helps alleviate the diameter reduction problem as well as the problem of open-flow annular space. However, in some applications additional problems can arise. If the well is not in good gauge, for example, there can still be communication of well fluids external of the tubular completion. There may also be limits on the types of completions that may be utilized.
The present invention features a technique for reducing or eliminating the diameter reduction and annular space problems without incurring the difficulties of previously attempted solutions. The technique utilizes an insertion guide that is introduced into an open-hole section of the wellbore. The insertion guide is moved through the wellbore in a contracted state. Once placed in its desired location, the insertion guide is expanded, e.g. deformed, radially outwardly at least partially against the formation, i.e. against the wall of the wellbore. Subsequent to expansion of the insertion guide, a final completion element, e.g. a tubular completion component, is deployed within the insertion guide.
Typically, the outside diameter of the completion element is selected such that it is nearly equal to the inside diameter of the insertion guide subsequent to expansion. Thus, the outside diameter of the completion element diameter is nearly equal the nominal inside diameter of the open-hole reduced only by the thickness of the wall of the insertion guide. Consequently, the completion element is readily removable while having a larger diameter than otherwise possible. Additionally, the detrimental annular space is substantially if not completely eliminated.